1. Field of the Invention
The Present invention relates to transducer systems for sensing pressure.
2. Background Art
Pressure sensitive transducers generate a signal indicative of the amount of pressure applied to a flexible membrane. Such transducers may also generate a signal based on the location of pressure applied to the flexible membrane. Such pressure sensitive transducers provide inputs for a wide variety of applications such as remote controls, game controllers, mouse pads, tactile sensors, and the like. Pressure sensitive transducers are typically coupled with electronics that condition and amplify pressure signals.
Various constructions for pressure sensitive transducers are possible. One type includes one or more force sensing resisters (FSRs). Various FSRs have been disclosed, such as those described in commonly assigned U.S. Pat. Nos. 4,314,227; 4,314,228; and 4,489,302; each of which is hereby incorporated by reference in its entirety. Typically, an FSR is composed of three parts, a rigid base, a spacer, and a resistive membrane. Conductive traces are typically arranged in separated interdigitated sets on the base. These traces may be configured in a single zone or in multiple zones to allow, for example, pointing devices as described in commonly assigned U.S. Pat. Nos. 5,659,334 and 5,828,363, each of which is hereby incorporated by reference in its entirety. The flexible resistive membrane is spaced apart from the base layer by a spacer, which is typically a ring of material around the outer edge of the conductive traces. The spacer is also typically coated with adhesive to hold the device together. The flexible top membrane may be made of a polymer coated on its inner face with semi-conductive or resistive ink, giving the FSR force sensing properties. This ink is described in commonly owned U.S. Pat. Nos. 5,296,837 and 5,302,936, each of which is hereby incorporated by reference in its entirety.
In most practical applications, the FSR must be connected to sensing and conditioning electronics in order to effectively operate. One way this may be accomplished is by connecting the FSR to a printed circuit board containing the electronics with a multi-conductor cable. Another way of connecting the FSR to support electronics is to adhere the FSR base directly to the circuit board containing the electronics. Electrical connection may be made between traces on the FSR and corresponding traces on the printed circuit board using z-tape, which only conducts in a direction perpendicular to the tape surface. While either method is effective, both have unnecessary manufacturing steps and require unnecessary components, thus increasing the cost of a pressure sensitive transducer system as well as increasing the likelihood of system failure. What is needed is a pressure sensitive transducer and a method for making such a transducer that requires fewer components and fewer manufacturing steps without sacrificing transducer performance.